The early elementary school years are widely understood to be critical to a child developing a strong foundation for future academic success. Children arrive at kindergarten from diverse settings and experiences, and not all of them are "kindergarten ready." Kindergarten readiness refers to the skills and abilities needed to succeed in school, including social and emotional development, language acquisition, physical well-being, and motor skills. The Department of Education estimated that about 3.3 million children enrolled in public kindergarten in fall 2024; however, kindergarten is not universally required. States determine whether school districts must offer kindergarten and whether kindergarten attendance is mandatory. States also have discretion regarding whether, and how, to assess children's kindergarten readiness. Consequently, little is known about kindergarten readiness levels nationwide. The authors were asked to provide information about which states assess children's readiness to learn upon entering kindergarten. For this report, they surveyed state education and early childhood officials in all 50 states and the District of Columbia on how they collect and use kindergarten readiness information for children attending public schools. Throughout this report, the authors refer to all 51 survey respondents as states. They also held discussion groups with kindergarten teachers in six states to provide information about their experiences with administering and using assessments in kindergarten, among other topics.